1. Field of the Invention
This invention generally relates to work holders, and more particularly, to an improved work holder for a cutting or shearing machine or the like.
2. Description of the Prior Art
When relatively large, flat, thin flexible sheets of metal, plastic or the like are cut or sheared in a cutting or shearing machine, some difficulty is normally encountered because of sagging or bending of the portion to be cut or sheared before that operation takes place. Thus, although most of the sheet is supported on a table or platform outside the machine as it is being advanced to the machine's cutter, the end of the sheet that is fed into the machine between the cutter and the backstop of the machine is unsupported by the machine so that when it is cut it can drop away and clear the cutting area for the next portion to be advanced. It is that unsupported portion which tends to sag or bend. The sagging or bending interferes with properly executing clean, flat, sharp, accurate cutting of the sheet.
It would therefore be desireable to provide a simple, durable, inexpensive work holder which could give the sheet portion to be cut adequate support before and during cutting but which could be easily and temporarily removed to allow the cut-piece to drop away. Such a device should be capable of quick and ready manipulation to match the operation of shearing mills and the like.
Various supporting and holding mechanisms have been devised for specialized uses relating to the automobile manufacturing and repair industries. For example, U.S. Pat. No. 3,752,463 of Schilke and U.S. Pat. No. 4,029,308 of Mathers disclose respective devices particularly suited for use in handling hoods of motorized vehicles. U.S. Pat. No. 2,825,477 of Ross and U.S. Pat. No. 2,938,635 of Dyer disclose support mechanisms for facilitating removal, repair and replacement of vehicle engines, and may include a jack arrangement for lifting and supporting the vehicle as well as the engine during the automotive service operation. U.S. Pat. No. 2,827,690 of Brown and U.S. Pat. No. 4,183,511 of Marek relate to specialized holders for vehicle body panels, more specifically vehicle doors, during removal and repair operations.
All of these devices and mechanisms are particularly adapted to the singularly specialized functions which they are designed to perform. Most of them have particular elements incorporated in the mechanisms to facilitate their function, as for example wheels for moving jacks about, legs and frames for stands, arms or the like for positioning the particular items to be supported in the proper orientation to facilitate removal from or installation in or on a vehicle, gripping means, such as the suction cups of the Marek patent, for holding the supported device, and the like. Each of the structures of these respective patents is especially designed for a given function and is not adaptable to another, unrelated function.
Other patents which are known in the field of lifting and supporting mechanisms are the Schiltz U.S. Pat. No. 2,116,251 and the Crosslin U.S. Pat. No. 2,695,759. The Schiltz patent discloses a workholder for metal cutting machines which is designed to hold a workpiece in firm relationship to a machine for shaping the workpiece. The Crosslin patent discloses a lifting device for fiberboard, e.g. Sheetrock, in a manner which enables one man to operate it to move a fiberboard into position in a ceiling area and thereafter hold it in place while it is secured.
None of the prior art patents known to applicant discloses any mechanism remotely related to dealing with the problem faced by applicant in developing the structure of the present invention.